Spark plug



SPARK PLUG Filed March 23, 1944 ?6 !NVENTOR Jos-, H OC 0/ TONA.

BY U W/TNESS." VJ/ y ATTORNEYS Patented Nov. 6, 1945 UNITED STATESPATENT OFFICE SPARK PLUG Joseph O. O. di Tona, Newark, N. J. ApplicationMarch 23, 1944, Serial No 527,715

7 Claims.

This invention relates to improvements in spark plugs.

The primary object of the invention resides in a spark plug in which thesame is sealed against the leakage of combustible fuel gasestherethrough, thus preventing loss of compression When the spark plug isin use upon an internal combustion engine.

Another feature of the invention is to provide a sealed spark plug whichis simple of Construction and assembly, inexpensive to manufacture, andstrong and durable to withstand the extreme temperatures and pressurewhen in use.

Other nove] features of the invention will become apparent as thefollowing specification is read in conjunction with the accompanyingdrawing, in which,

;Figure 1 is a side elevational View of my improved spark plug, theterminal clamping nut being shown in dotted lines.

Figure 2 is an enlarged vertical longitudinal sectional View taken onthe line 2--2 of Figure l.

Figure 3 is an enlarged horizontal sectional View on the line 3-3 ofFigure 1.

Referring to the drawing by reference characters, the numeral lodesignates my improved spark plug in its entirety. The spark plug IDcomprises a conventional spark plug shell or plug base H, the same beingmade of metal and comprising an externally screw-threaded body portion|2 and a reduced screw-threaded plug portion [3, there being a fiange orshoulder 14 intermediate the portions l2 and 3. The plug-like body ll isprovided with an axial stepped bore which consists of an inner boreportion !5 and a reduced bore portion !6, the stepped portionconstituting a shouldered seat Il. A ground electrode [8 is provided atthe outer end of the reduced bore portion I 6. The inner face of thebase member H is provided with an annular groove !9 which is concentricto the bore and is disposed adjacent the enlarged portion !5 thereon.Seated in the groove !9 is one end of a collar 20, said collar being ofmetal to which glass may be bonded for reasons to be hereinafterexplained. That portion of the collar which is seated in the groove !9is brazed to the base member I I to provide a rigid sealed jointtherebetween. The base member H and the collar 20 constitute a singleunit for reasons of assembly.

A second assembly unit consists of the lead or central electrode 2lwhich carries a metal cupshaped member 22. The electrode 2| comprises acylindrical body portion 23, a reduced threaded extension 24 and areduced cylindrical stem portion 25, the free terminal end of theportion 25 being provided with a tungsten sparking tip 26. Thecup-shaped member 22, like the collar 20, is made of a metal to whichglass may be bonded, the end wall of the cup-shaped member 22 having acentral opening through which the body portion 23 of the electrodepasses, said cupshaped member being brazed to the portion 23 to providea rigid sealed joint.

The numeral 21 designates an inner insulating core made of any wellknown refractory material capable of withstanding temperatures above1800 F. without undergoing physical or chemical changes. The core 2'! ismolded and is provided with an axial bore 28 which extends the lengththereof. The main body portion of the core 21 is of a diameter to fitinto the enlarged bore portion !5 and is provided with a reduceddownwardly tapered portion 29 which extends into the reduced boreportion !6. The body portion of the core 21 and the reduced portion 29form a shoulder 30 which is complementary to the shouldered seat Il. Acopper scaling Washer 3l is interposed between the shoulder 30 and theseat H for sealing the joint therebetween. The Washer 3! is preferablyconstructed of beryllium copper although other equivalent materials maybe used in lieu thereof.

The reduced stem portion 25 of the central electrode 2l extends throughthe bore 28 of the core 21 With the tip end 25 extending beyond thelower end of the core and in suitable spaced sparking distance from theground electrode 26, the space between the electrodes constituting thesparking gap. The upper end of the bore 28 is slightly enlarged toprovide a shouldered seat 32 which is confronted by shoulder 33 formedbetween the body portion 23 and the reduced stem 25 of the centralelectrode. A copper sealing Washer 34 is interposed between the shoulder33 and the seat 32 to seal the joint therebetween. The copper Washer 34might also be made of beryllium or equivalent material.

With the parts in the assembled position so far described, it will benoted that the annular side wall or fiange 35 of the cup-shaped member22 is in spaced confronting and concentric relation with respect to themetal collar 23. Bonded to the flange 35 and collar 20 are therespective ends of a glass connecting sleeve 36. The bonds between theglass sleeve and the flange 35 and collar 20 are airtight whereupon thespace between the inner core 27 and sleeve SG is hermetically sealed.

Screwed to the threaded portion !2 is one end of an outer metalprotecting shield or casing 3?, the other end of said shield beingexternally screw-threaded as at 38. Interposed between the protectingshield 31 and the glass sleeve 36 is the cylindrical skirt portion 39 ofan outer insulating core 40 which is also constructed of a reractorymaterial capable of withstanding high temperatures. The upper end of thecore 40 is provided with an annular fiange GI which rests upon the upperedge of the outer casing 31: The

, threaded end 24 of the electrode 23 passes.

outer core 40 is provided with a central passage 42 through which thebody portion 23 of the central electrode passes. For the purpose ofholding the core 40 in position and for closing the upper end of theprotective casing 31 there is a plastic insulating cap 43, the samebeing screwed to the threaded portion 38. The cap 43 is provided with acentral opening 44 through which the outer clamping nut or snap adapterfor a lead wire is applied to the threaded portion 24, such clamping nutbeing shown in dotted lines at 45 in Figura 1.

From the foregoing description, it is seen that I have provided a sparkplug for internal combustion engines in which the joints between theparts are sealed against the escape of fuel gases during the compressionstroke of the motor. The parts and joints are of sufiicient strength towithstand the extreme temperatures and pressures to which they areexposed during use.

While I have referred to certain of the parts as being constructed ofspecific materials, the materials may vary without in any way departingfrom the scope of the invention set forth in the appended claims. i

Having thus described the invention, what I claim as new and desire tosecure by Letters Patent, is:

' l; A spark plug comprising a screw base having a ground electrode, acasing having one of its ends threaded to said base, an end closurethreaded to the other end of said casing, a lead electrode mountedaxially within said casing having one of its ends in spaced relation tothe ground electrode and its other end extending beyond said endclosure, insulating means within said casing for shielding said leadelectrode, and a sealed chamber within said casing between the base andthe end closure through which said lead electrode passes.

2.' A spark plug comprising a screw base having a stepped central'boretherein, the stepped portion consituting a shoulder seat,` a groundelectrode on said base, an insulating core having a shoulder in sealingrelation to the shoulder seat, said core having an axial bore extendingthe length thereof, a lead electrode extending through said axial borehaving its inner end in spaced relation to said ground electrode and itsouter end extending beyond the outer end of the core, a fixed concentriccollar extending inwardly from the base in spaced relation to said core,a cup-shaped member fixedly Secured to the lead electrode with its openside disposed'in confronting relation to said collar and spacedtherefrom, and a glass sleeve having its ends respectively connected andsealed to the collar and cup- 'shaped member and spaced from said core.

3. A spark plug as set forth in claim 2 including an outer protectingshield having one' end threaded to the base, said shield being spacedfrom the sleeve in surrounding relation, and a cap threaded to the otherend of the shield having a central aperture for the passage of the outerend of the lead electrode.

4. A spari; plug as set forth in claim 2 includin:: an outer shieldcasing having its inner end threaded to the base, a hollow outerinsulating core mounted within said casing in spacedrelation thereto andin spaced encircling relation to the sleeve, and a cap threaded to theouter end of said casing, said outer core and cap having 2,3s8,472 i fTing its inner end seated in said groove and fixedly sealed to the base,an inner insulating core having a central bore extending therethrough,said inner core having a reduced inner end portion, the reduced endportion defining a shoulder disposed in confronting relation to theshoulder seat; a sealing Washer interposed between the shoulder and saidshoulder seat, a central electrode having a reduced portion extendingthrough the bore in said inner core, the free end of the reduced portionconstituting a sparking tip, a ground electrode on said base in spacedrelation to the sparking tip of the central electrode, the

reduced portion of the central electrode defining' a shoulder, ashouldered seat provided on the outer end of the inner core inconfronting relation to the shoulder on the electrode, a sealing Washerinterposed between the last-mentioned shoulder and shoulder seat, ametal cup-shaped member integrally connected to said central electrodeconcentric thereto with its open side arranged in spaced confrontingrelation to said collar, a glass sleeve having ,its respective endssealingly connected to the cup-shaped member and to the collar, saidglass sleeve surrounding the inner core in spaced relation thereto, anouter insulating core surrounding said glass sleeve and having a flangeseated on the outer end of the casing, a shield casing having its innerend threaded to said screw base, and an insulating cap threaded to theouter end of said casing in clamping engagement with the outer core,said outer core and cap having alined apertures therein 'for the passageof the outer end of the central electrode.

6. In a spark plug, a screw base having a central bore therein and aground electrode at the outer end thereof, an insulating core having anaxial bore extending the length thereof and its lower end extending intosaid bore, sealing means between said core and the walls of said bore, alead electrode extending through said axial bore having its lower enddisposed in spaced relation to said ground electrode and its other endextending beyond the outer end of the core, a fixed concentric collarextending upwardly from the base in spaced relation to said core, acup-shaped member xedly secured to said lead electrode with its openside disposed downwardly in confronting relation to said collar andspaced therefrom, and a glass sleeve having its ends respectivelyconnected and sealed to the collar and cupshaped member and spaced fromsaid core.

'7. In a spark plug as set forth in claim 6, including a cylindricalcasing having its lower end threaded to said screw base and disposed inspaced concentric relation to the glass sleeve, a cylindrical insulatingmember telescoping the sleeve having its lower end abutting the screwbase, an annular fiange at the upper end of the insulating memberoverlying the top edge of said casing, and a cap threaded to the upperend of the casing and orcibly hearing against the top of the insulatingmember to hold the lower end thereof tight against the screw base.

JOSEPI-I O. C. DI TONA.

